Stability of Actinolite on Venus

Venus currently has a hostile surface environment with temperatures of ~460 C, pres-sures near 92 bars, and an atmosphere composed of super critical CO2 hosting a myriad of other potentially reactive gases (e.g., SO2, HCl, HF). However, it has been proposed that its surface may not have always been so harsh. Models suggest there may have been billions of years of clement conditions allowing an Earth-like environment with liquid water oceans. If such conditions existed, it is possible Venus formed a similar array of hydrous or aqueous minerals as seen on other planets with liquid surface water (e.g., Mars, Earth). Based on thermodynamic modeling, many of these phases would not be stable under the current atmospheric conditions on Venus, dehydrating due to the high temperatures and low concentration of H2O in the atmosphere. However, the rate of decomposition of these phases may allow them to remain present on the surface over geologic time. For example, experiments on the reaction rate of tremolite (Ca2Mg5Si8O22(OH)2) show a 50% decomposition time of 2.7 Gyr for micrometer sized grains in unreactive atmospheres (i.e., without SO2) at 740 K, and a 50% decomposition time of 70 Gyr for crystals several millimeters to centimeters in size. If hydrous minerals can remain on the surface of Venus over geologic time, it has implications for our detection of evidence of these past environments, and also for the overall water budget of the planet. If after surficial dehydration the planet was able to still store water in its crust, possible processes such as subduction or metamorphism could still have operated using stored water long after liquid surface water evaporated. Several previous studies have focused on experimental investigations of mineral stability on Venus. In particular, the works of studied the decomposition rate of tremolite under conditions relevant to Venus. As their focus was on decomposition of the mineral due to lack of water in the atmosphere, their experiments were undertaken using only CO2 or N2 gas at atmospheric pressure. Re-cent experiments have examined reactivity of other minerals with the Venusian atmosphere using more complex gas compositions at similar pressures to those seen on Venus. These studies show reaction of silicate minerals with atmospheric components on relatively short timescales (i.e., on the order of days). The reported reactions of silicate materials in both studies produced iron oxides, Ca sulfates, and Na sulfates. These ions are present in many amphiboles, and Ca was proposed by Johnson and Fegley to potentially have an important role in the decomposition mechanism for tremolite, with the Ca-O bond being the first to break during decomposition. The potential involvement of Ca in both processes raises the question of whether or not the reaction to form a secondary mineral phase will influence the rate of amphibole break-down (e.g., discussion in for tremolite). Additionally, reaction of Ca with atmospheric gases may result in a different secondary mineral assemblage than simple amphibole decomposition, which will need to be recognized when searching for evidence of past hydrated minerals on the Venusian surface. In order to understand the effect of this reaction on the overall preservation potential of amphibole on the surface of Venus, we are conducting experiments in both reactive and nonreactive atmospheres using the mineral actinolite (Ca2(Mg,Fe)5Si8O22(OH)2), an amphibole with similar crystal structure to tremolite that contains both Ca and Fe

Metabolipidomic profiling reveals an age‐related deficiency of skeletal muscle pro‐resolving mediators that contributes to maladaptive tissue remodeling

Specialized pro- resolving mediators actively limit inflammation and support tissue regeneration, but their role in age- related muscle dysfunction has not been explored. We profiled the mediator lipidome of aging muscle via liquid chromatography- tandem mass spectrometry and tested whether treatment with the pro- resolving mediator resolvin D1 (RvD1) could rejuvenate the regenerative ability of aged muscle. Aged mice displayed chronic muscle inflammation and this was associated with a basal deficiency of pro- resolving mediators 8- oxo- RvD1, resolvin E3, and maresin 1, as well as many anti- inflammatory cytochrome P450- derived lipid epoxides. Following muscle injury, young and aged mice produced similar amounts of most pro- inflammatory eicosanoid metabolites of cyclooxygenase (e.g., prostaglandin E2) and 12- lipoxygenase (e.g., 12- hydroxy- eicosatetraenoic acid), but aged mice produced fewer markers of pro- resolving mediators including the lipoxins (15- hydroxy- eicosatetraenoic acid), D- resolvins/protectins (17- hydroxy- docosahexaenoic acid), E- resolvins (18- hydroxy- eicosapentaenoic acid), and maresins (14- hydroxy- docosahexaenoic acid). Similar absences of downstream pro- resolving mediators including lipoxin A4, resolvin D6, protectin D1/DX, and maresin 1 in aged muscle were associated with greater inflammation, impaired myofiber regeneration, and delayed recovery of strength. Daily intraperitoneal injection of RvD1 had minimal impact on intramuscular leukocyte infiltration and myofiber regeneration but suppressed inflammatory cytokine expression, limited fibrosis, and improved recovery of muscle function. We conclude that aging results in deficient local biosynthesis of specialized pro- resolving mediators in muscle and that immunoresolvents may be attractive novel therapeutics for the treatment of muscular injuries and associated pain in the elderly, due to positive effects on recovery of muscle function without the negative side effects on tissue regeneration of non- steroidal anti- inflammatory drugs.Chronic low- grade inflammation of aging muscle was associated with a basal deficiency of maresin 1, resolvin E3, 8- oxo- resolvin D1, and anti- inflammatory fatty acid epoxides. Aged mice produced normal amounts of most prostaglandins following muscle injury but were deficient in local biosynthesis of markers of the lipoxins, E- resolvins, D- resolvins, and maresins. Systemic treatment with resolvin D1 suppressed inflammatory cytokine expression, limited muscle fibrosis, and improved functional recovery.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168317/1/acel13393-sup-0002-TableS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168317/2/acel13393-sup-0003-TableS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168317/3/acel13393_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168317/4/acel13393-sup-0001-FigS1-S4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168317/5/acel13393.pd

Genome-wide association meta-analysis identifies five modifier loci of lung disease severity in cystic fibrosis

The identification of small molecules that target specific CFTR variants has ushered in a new era of treatment for cystic fibrosis (CF), yet optimal, individualized treatment of CF will require identification and targeting of disease modifiers. Here we use genome-wide association analysis to identify genetic modifiers of CF lung disease, the primary cause of mortality. Meta-analysis of 6,365 CF patients identifies five loci that display significant association with variation in lung disease. Regions on chr3q29 (MUC4/MUC20; P=3.3 × 10(−11)), chr5p15.3 (SLC9A3; P=6.8 × 10(−12)), chr6p21.3 (HLA Class II; P=1.2 × 10(−8)) and chrXq22-q23 (AGTR2/SLC6A14; P=1.8 × 10(−9)) contain genes of high biological relevance to CF pathophysiology. The fifth locus, on chr11p12-p13 (EHF/APIP; P=1.9 × 10(−10)), was previously shown to be associated with lung disease. These results provide new insights into potential targets for modulating lung disease severity in CF